From Your perspective You told (as in his shoes), I must say it is even more stupid to count on a one time bang instead of a sustainable income (with potentional multiplicators) and it seems a lot of other devs have a blind spot in Math regarding this too, despite they are very skilled in numbers, a lot of devs arent able to conclude economically sober.
That's really weird and wasted potential.
As I understand what you're saying, this dude did get burnout sure. I think doing a solo job is crazy, but what he would post, and the things he was doing when he was "ill" was kinda bs. To say you're taking a break cause you're sick is fine, but this dude was blowing through that money on alcohol and all kinds of stuff. He would silence anyone that asked about the game, I mean it seemed promising when he kept with this monthly update page on his discord for a solid 3 months, and then he just vanished. Also that 3k is a massive drop in his original monthly take, im glad maybe he will either truly quit, or stick to one project, and not try to do some weird thing with making 9 different games, etc.